There is a wide variety of additives for of stabilizing PVC. Particularly suitable for this purpose are compounds of lead, of barium and of cadmium, but nowadays these are contentious for environmental reasons or due to their heavy metal content (cf.,pages 303-311, and "Kunststoff Handbuch PVC" ["Plastics Handbook PVC"], Vol. 2/1, W. Becker/D.Braun, Carl Hanser Verlag, 2.sup.nd Ed., 1985, pages 531-538; and also Kirk-Othmer: "Encyclopedia of Chemical Technology", 4.sup.th Ed., 1994, Vol. 12, Heat Stabilizers, pp. 1071-1091). Further attempts are therefore being made to find effective stabilizers or stabilizer combinations which are free from lead, barium and cadmium.
1,3-disubstituted aminopyrimidinediones have already been described in U.S. Pat. No. 3,436,362, U.S. Pat. No. 4,656,209, U.S. Pat. No. 4,352,903 and EP-A-0 768 336, and can be prepared by known methods in one (or more) steps.
It has now been found that 1,3-disubstituted 4-aminopyrimidinediones and oxazolidino-4-aminopyrimidinediones of the general formulae I and II and particularly suitable for stabilizing chlorine-containing polymers, in particular PVC.